For service and parts needs, visit your dealer. You will receive genuine GM parts and GM-trained and supported service people.
Genuine GM parts have one of these marks:

Vehicle Care
California Proposition 65 WarningShock Absorber Disposal
Warning: Use the proper eye protection when drilling to prevent
metal chips from causing physical injury.
Clamp the strut in a vise horizontally with the rod ( 1) completely
extended.
Drill a hole in the strut at the center of the end cap (3) using a 5 mm
(3/16 in) drill bit. Gas o ...
Navigation
OnStar navigation requires the Directions and Connections service plan.
Press to receive directions or have
them sent to the vehicle navigation screen, if equipped.
Destinations can also be forwarded to the vehicle from MapQuest.com.
The OnStar mapping database is continuously updated. For cov ...
Buying New Tires
GM has developed and matched specific tires for the vehicle. The original equipment
tires installed were designed to meet General Motors Tire Performance Criteria Specification
(TPC Spec) system rating. When replacement tires are needed, GM strongly recommends
buying tires with the same TPC Sp ...